package linkedlist.passed2;

/**
 * @author xyyi
 *
 */
public class AddTwoNumbers {
	/**
	Add Two Numbers
	You are given two linked lists representing two non-negative numbers. 
	The digits are stored in reverse order and each of their nodes contain a single digit. 
	Add the two numbers and return it as a linked list.

	Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
	Output: 7 -> 0 -> 8
	 */
	
    public ListNode addTwoNumbers1(ListNode l1, ListNode l2) {
        if (l1 == null)
            return l2;
        if (l2 == null)
            return l1;
        ListNode dummyHead = new ListNode(-1);
        ListNode currNode = dummyHead; //pitfall need to remember currNode
        int carry = 0;
        while (l1 != null || l2 != null || carry > 0) {
            int val1 = l1 != null ? l1.val : 0;
            int val2 = l2 != null ? l2.val : 0;
            int sum = val1 + val2 + carry;
            carry = sum / 10;
            currNode.next = new ListNode(sum % 10);
            currNode = currNode.next;
            //pitall: need to check null and move forward.
            l1 = l1 != null ? l1.next : null;
            l2 = l2 != null ? l2.next : null;
        }
        
        return dummyHead.next;
    }
    
	public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
		if (l1 == null)
			return l2;
		if (l2 == null)
			return l1;

		ListNode dummyNode = new ListNode(-1);
		ListNode currNode = dummyNode;
		int carry = 0;
		while (l1 != null || l2 != null || carry != 0) {
			int sum = 0;
			if (l1 != null) {
				sum = sum + l1.val;
				l1 = l1.next;
			}
			if (l2 != null) {
				sum = sum + l2.val;
				l2 = l2.next;
			}
			sum = sum + carry;
			carry = sum / 10;
			sum = sum % 10;
			currNode.next = new ListNode(sum);
			currNode = currNode.next;
		}

		return dummyNode.next;
	}

	/**
	 * Definition for singly-linked list.
	 */
	public class ListNode {
		int val;
		ListNode next;

		ListNode(int x) {
			val = x;
			next = null;
		}
	}

	public AddTwoNumbers() {
		// TODO Auto-generated constructor stub
	}

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub

	}

}
